1. Field of the Invention
This invention relates to a method for the production of a standard oxide sample for the determination of impurity elements contained in inorganic compounds such as raw material powders of refractory carbides, nitrides and borides, single crystals, oxides for the production of superconductors, and other industry grade oxides, by X-ray fluorescence spectrometry.
Such inorganic compounds contain minute amounts of various impurity elements such as chromium, manganese, iron, cobalt and nickel. In the production of a high-temperature superconductor from such a refractory inorganic compound, it is essential to be able to accurately determine the minute amount of impurity elements, in the compound.
2. Prior Art Statement
As observed in the process for determination of impurity elements in industry grade oxides, the determination of the impurity element content of a refractory inorganic compound has heretofore been performed by the method of chemically separating the inorganic compound into its main component element and its impurity elements (so as to reduce the effect of the large amount of main-component element) and then determining the impurity element content by ICP emission analysis or other spectroscopic analysis technique.
From the standpoint of the determination procedure, the chemical separation of the main element of the refractory inorganic compound from the minute amounts of impurity elements contained in the compound is extremely difficult, consumes much time, and is susceptible to experimental error.
In contrast, the nature of characteristic X-rays is such that even when the X-ray fluorescence is generated in the presence of large amounts of main-component elements, the characteristic X-rays of the impurity elements can be selectively determined within a range not affected by the main-component elements, with enhanced accuracy and reduced time consumption. Thus, X-ray fluorescence spectrometry is a suitable method for determination of minute amounts of impurity elements contained in the refractory inorganic compounds mentioned above.
In the method of X-ray fluorescence, the minute amounts of impurity elements have to be determined using calibration curves obtained using standard samples produced in advance. However, no one has ever produced the standard samples necessary for the determination of the impurity elements contained in the refractory inorganic compound by the method of X-ray fluorescence spectrometry.
The present inventors conducted a study on methods for effective solution of samples and conducted experiments using thermal decomposition curves, for the purpose of enabling the production of standard samples for determination of impurity elements in refractory inorganic compounds by the method of X-ray fluorescence spectrometry. This invention has been perfected as a result.